Method for producing a filter element

ABSTRACT

The invention relates to a method for producing a filter element for filtering fluids, such as hydraulic fluids, lubricants, or fuels, comprising the following steps: a) providing at least one section of a filter mat web ( 14 ) made of one or more layers of at least one filter medium; b) connecting the ends of the at least one section in order to form an annular body ( 12 ) and placing said annular body onto a support pipe ( 16 ); wherein said method is characterized by: c) wrapping at least one cutout of a film web ( 8 ) around the outside of the annular body ( 12 ) located on the support pipe ( 16 ) and d) placing end areas ( 24 ) of the at least one cutout of the film web ( 8 ) one on top of the other and connecting the overlapping end areas ( 24 ).

The invention relates to a method for producing a filter element forfiltering fluids, such as hydraulic fluids, lubricants, or fuels, saidmethod comprising the steps of providing at least one section of afilter mat web made of one or more layers of at least one filter medium;connecting the ends of the at least one section in order to form anannular body; and placing said annular body onto a support tube.

Filter elements, which are used in industrial systems to remove theimpurities from fluids that are used in the ongoing operations, areknown from a number of prior art embodiments. For example, document EP 1015 095 B1 shows an advantageous design that has become very popular andis used extensively in pertinent systems. If in operation the filter matbecomes completely clogged with impurities, the filter element has to bechanged for a new and unconsumed filter element. In light of theextensive use of such filter elements, it is necessary to have a largequantity of filter elements for the initial setup and replacement, sothat such filter elements can be referred to as so-called “mass producedarticles.” Hence, a simple and efficient production of the filterelements is of considerable economic importance.

According to the state of the art described in document EP 1 015 095 B1,the filter element, which is provided with an outer sleeve made of aperforated film web, is produced in such a way that a closed cylinder ismade of a film web forming the outer sleeve. In this case, theoverlapping ends of the film web are connected by means of alongitudinal weld; and then the annular body is introduced into thecylindrical outer sleeve. In order to facilitate the introduction, thepleats are gathered together at the frontal end of the annular body insuch a way that the result is an insert cone that facilitates theintroduction into the cylindrical outer sleeve.

Based on the aforesaid, the object of the present invention is toprovide a method that makes it possible to produce such filter elementsin a very efficient and economical way.

The present invention achieves this object with a method that comprisesthe process steps a) to d) specified in claim 1.

This is done in such a way that an outer sleeve of the filter element isformed on a pre-assembled annular body, which is made of a pleatedfilter mat web and is located on an inner support tube, in that at leastone initially flat blank of a film web is placed around the annularbody; and thereafter the overlapping end areas are connected together.

The inventive procedure, wherein the film web is placed around theexterior of the annular body and only then is the connectinglongitudinal weld formed, constitutes a simplification compared to theprior art, and this simplification in turn leads to a reduction in theproduction costs. The end areas of the film web or more specifically theend areas of the at least one blank of the film web are typicallyconnected together by forming a longitudinal weld. Depending on thefilter element to be produced, the support tube can have fluid openings,and/or the film web can be made with perforations. Advantageousembodiments of the method according to the invention are the subjectmatter of the dependent claims.

An especially advantageous approach may be to proceed in such a way thatthe at least one blank of the film web is clamped around the annularbody before the end areas of the blank are connected. As a result, theprestress of the filter mat is no longer dependent on the position oftolerance (pleat height) of the filter mat, so that the result is anadditional simplification of the production. Since there is no longerany friction between the outer sleeve and the filter mat because of theelimination of an axial insert movement despite the prestress achievedin the finished state, there is no abrasion. Moreover, there is no needfor an after-treatment, such as in the form of shrinking on the film, inorder to achieve a desired prestress of the outer sleeve, so that thereis no thermal degradation of the filter mat web.

Preferably, the connecting of the overlapping end areas is carried outby a thermal joining procedure. If the film that forms the outer sleeveis made of a polyamide compound or a polyethylene compound or if thefilm is made of polyester or epoxy polyurethane or a similar syntheticplastic material with good hot adhesive properties, then joining can becarried out by an ultrasonic welding process or by means of a weldinglaser.

In the latter case, the laser welding operation can be carried out usingan additional laser-impermeable barrier layer, if the material of thefilm itself does not form a suitable laser-impermeable barrier layer.

Given suitable materials, the welding operation can be carried outwithout a welding filler, whereas as an alternative a welding filler isinserted between the overlapping end areas before the welding operation.

In this context, it is especially advantageous that a film that servesas the laser-impermeable barrier layer can be used as the weldingfiller.

One approach with respect to wrapping the annular body with the film canbe to use movable molded bodies that act on the initially flat film webby means of infeed movements and that form the film web around theannular body. In this case, the infeed movements can be moved with thecomponents extending in the circumferential direction so that, when thefilm web is wrapped around the annular body, said film web is clamped.

According to claim 11, the subject matter of the invention is also afilter element, which is produced according to the method disclosed inone of claims 1 to 10.

The invention is explained in detail below with reference to thedrawings. Referring to the drawings:

FIG. 1 is a perspective view of a filter element that is producedaccording to the method of the invention;

FIG. 2 is a perspective oblique view in the direction of the end sectionof the filter element from FIG. 1 that is depicted without theassociated end caps;

FIG. 3 is a highly enlarged detail of the area designated as III in FIG.2;

FIG. 4 is a highly simplified perspective view in schematic form of aprocessing system with the molded bodies located in a starting position;and

FIG. 5 is a front view of the system from FIG. 4 with the molded bodieslocated in a closed working position in operating state.

The filter element 2, depicted in its entirety in FIG. 1, has an outersleeve, which is made of a perforated film web 8, between the end caps 4and 6, which are injection molded of a synthetic plastic material. Theperforation of the film web 8 is indicated only in a few areas that aredesignated as 10. The film web 8 surrounds an annular body 12 having aconstruction that is most easily discernible from FIGS. 2 and 3. Asevident, the annular body 12 has a folded filter mat web 14, which isfolded in the manner of pleats and surrounds an inner support tube 16having fluid openings. FIG. 3 shows that the ends 18 and 20 of the filmweb 8 are laid one on top of the other, so that an overlapping area 24is formed, in which the formed outer sleeve is closed in a longitudinalweld 22 (see FIGS. 1 and 2).

FIGS. 4 and 5 are in each instance a highly simplified view in schematicform of a processing system for carrying out the method according to theinvention. It is clear from FIG. 4 that the film web 8 which is locatedinitially in the form of a flat blank below the pre-assembled annularbody 12, comprising the filter mat 14 surrounding the support tube 16.The system has a movable lower molded body 26 and movable upper moldedbodies 28 and 30. Then in FIG. 4, the film web 8 is moved upward bymeans of the infeed fingers (not illustrated) and placed against theexterior of the annular body 12. Then the lower molded body 26 is movedupward in the direction of the movement arrow 32, while the upper moldedbodies 28 and 30 are moved—also in the direction of their allocatedmovement arrows 32—in the direction of the center of the annular body12, so that the system reaches the closed state that is shown in FIG. 5.In this state, the ends 18 and 20 of the film web 8 are placed, as shownin FIG. 3, one on top of the other in such a way that the overlappingarea 24 is formed, where a welding operation for forming a longitudinalweld 22 is carried out. Before this step takes place, that is, beforethe formed outer sleeve is closed, this outer sleeve is given aprestress, in that a tensile stress is produced in the film web 8 in thecircumferential direction. This can be done in any suitable way, forexample, in that a tensioning means (not illustrated) acts upon the ends18 and 20 of the film web prior to the overlapping; or when the uppermolded bodies rest against the exterior of the film web in the closedposition, as shown in FIG. 5, said upper molded bodies 28 and 30 performan additional movement in the direction of the curved arrows 34, bymeans of which the film web 8 is clamped.

Before the actual welding operation, the ends 18 and 20 of the film web8 are held together preferably by means of one or more pressure-applyingpieces 36. In the example described in the present case, joining is doneby laser welding using a laser unit 38 that can be moved according tothe movement arrow 32. It is clear from the drawing in FIG. 5 that thelaser unit 38 has a pressure-applying body 40 on the front end that canbe moved up against the overlapping area 24. This pressure-applyingbody, which is intended for laser light transmissive Plexiglas,compresses the welding area during the welding operation.

In the case of a film web 8 that is made of a synthetic plastic materialthat is not transmissive to laser light, and the film web 8 itself formsa laser-impermeable barrier layer that is appropriate for laser welding,the welding operation can be carried out without a welding filler, ifthe synthetic plastic material lends itself to a hot sealing procedure.Without a welding filler, the joining can also be performed byultrasonic welding instead of laser welding. However, a welding fillercan also be used, as in the case of the laser welding, for ultrasonicwelding in order to carry out a hot melt adhesive process. For the laserwelding operation, such a welding filler, which is designated as 42 inFIG. 3, can be inserted in the form of a strip of film in theoverlapping area 24 between the ends 18, 20 of the film web 8. In thiscase, it can be a film made of polybutylene terephthalate. Such a PBTfilm, which is sold under the tradename “Vestodur®,” can form a kind ofhot melt adhesive during the thermal welding operation. In addition,such a filler can serve as the laser-impermeable barrier layer that isopaque to laser light, if the welding operation is carried out by meansof laser welding.

The method disclosed in the claim provides the use of sections of afilter mat web 14 made of one or more layers of filter media that arefolded in the manner of pleats. In this case, the one layer can consistof a multilayer, where the stacked layers, which are laminated together,form together a tight composite.

The barrier layer under discussion can also be produced by depositingvaporized metals (sputtering) on the film or can be partially printed onsaid film.

1. A method for producing a filter element (2) for filtering fluids,such as hydraulic fluids, lubricants, or fuels, said method comprisingthe steps: a) providing at least one section of a filter mat web (14)made of one or more layers of at least one filter medium; b) connectingthe ends of the at least one section in order to form an annular body(12), and placing said annular body onto a support tube (16);characterized by: c) wrapping the exterior of the annular body (12),which is located on the support tube (16), with at least one blank of afilm web (8); and d) placing the end areas (24) of the at least oneblank of the film web (8) one on top of the other, and connecting theoverlapping end areas (24).
 2. The method according to claim 1,characterized in that the at least one blank of the film web (8) isclamped around the annular body (12) before the end areas (24) of theblank are connected.
 3. The method according to claims 1, characterizedin that the connecting of the overlapping end areas (24) is carried outby a thermal joining procedure (38).
 4. The method according to claim 3,characterized in that a film web (8) made of a synthetic plasticmaterial that is suitable for a welding process is used.
 5. The methodaccording to claim 3, characterized in that the connecting of theoverlapping end areas (24) is carried out by means of laser welding (38)using a laser-impermeable barrier layer (42).
 6. The method according toclaim 3, characterized in that the welding is carried out without awelding filler.
 7. The method according to claim 3, characterized inthat a welding filler (42) is inserted between the overlapping end areas(24) before the welding operation.
 8. The method according to claim 7,characterized in that a film (42) that serves as the laser-impermeablebarrier layer is used as the welding filler.
 9. The method according toclaim 1, characterized in that the wrapping of the annular body (12)with the film is carried out by means of the infeed movements of themolded bodies (26, 28, 30) that act upon the flat film web (8).
 10. Themethod according to one of claim 3, characterized in that, during thewelding operation, the overlapping end areas (24) of the film web (8)are pressed against each other by feeding in pressure-applying pieces(40).
 11. A filter element, which is produced according to the methodaccording to claim 1, and has an outer sleeve made of a film web (8),which is clamped around the exterior of an annular body (12) with afilter mat web (14).
 12. The filter element according to claim 11,characterized in that the film web (8) is made of a synthetic plasticmaterial.
 13. The filter element according to claim 11, characterized inthat the film web (8) is made with perforations.
 14. The filter elementaccording to claim 11, characterized in that the annular body (12) isplaced on a support tube (16) having fluid openings.